MORPHOLOGY OF THE ANAL SAC GLANDS OF THE OPOSSUM. (DIDELPHIS MARSUP-IALIS ?�vrRGINIANA

Abstract

The opossum, Didelphi$·marsupialis virgirtiana, is a useful laboratory animal •. As examples, it has·setved a~-the experimental subject·of significant contributio:p.s to marsupial reproduction (Selenka, 1885; -Hartm~n; . 1928 and·l952), embryonie developmerit (McCrady, 1938; New·and Mizell, 1972); foetal development (Block, 1964; Mizell, ·1968; Ulinski~ 1971; .Jurgelsl<.y, 1971) neuroanatomy ·a,nd neurophysiology (Krupp ·and :Quillen, 1964) .9-nd ·behavior · (McManus, 1970) • ~,:T~e. · oppssum also has' potential as a subject · for studies of bacterial endocarditis, glomerulonephrit:Ls, and amylo.idosis · (Sherwood,.l968). A colony of opossumswas maintained to'supply embryonie materi9-l for investigations of the yold ·sac 'placenta. ·. While ·h9-ndl:Lrig the opossums · it was observeq tha1; ;;:tvhen distressed, the oposso.m secretes a viscous, pale green to greenish yellow fluid·from two papillae loc~ted bilaterally at the anal ve_rge (Fig. 1). The·literature·on this glanc;l·is sparse.; Althöugh there are·reports of studies of.these'glands in other marsupials (Green; 1963; Munhoz and Merzel, 1967; Schultz-Westrum, 1969);. there are no reports :.on. the gland · in Didelphis ·ma.rsupialis virgirtiana.o Two·functions'have .. been attributed to 'the opossum' s. glaildular · sec:tetion: . · that it is used in· defense (McManus, · 1970); .or th,at it is. used ·for interspec.'if:Lc oifactory communication · (Schaffe~, 1940; Francq, .1969; and.Schultz-Westrum, .1969). · Except for some ob.lique: references in' a study of the· histochemistry'' of the_. gl9-nd in' a South American opossulll, D. aurita (Munhöz and Merzel, 1967), the secretion has ·not been charact~rized chemically _i:p. this or any · other marsupial. There are;sever9-l types· of anal gla.nds'fou:p.d·in Metather:La·and· Eutheria (Chatin, ·1874·;. Schaffer,' 1940; Green, 19.63; and ·McCöll, 1967) • ·